Magnetic core annunciator system



June 12, 1962 E. A. KELLER MAGNETIC CORE ANNUNCIATOR SYSTEM 3Sheets-Sheet 1 Filed Aug. 17, 1959 1N VENTOR. j/f

June 12, 1962 E. A. KELLER 3,039,085

MAGNETIC CORE ANNUNCIATOR SYSTEM Filed Aug. 17, 1959 5 Sheets- Sheet 2INVENTOR.

llaAw June 12, 1962 E. A. KELLER 3,039,085

MAGNETIC CORE ANNUNCIATOR SYSTEM Filed Aug. 17, 1959 3 Sheets-Sheet 3 44:gl/Z4 n, L I g I I I l /F Mc.

United States Patent G 3,039,0 MAGNETIC CORE ANNUNCATGR SYSTEM Ernest A.Keller, Wilmette, Ill., assigner, by mesne assignments, to ISI,Incorporated, Skokie, Ill., a corporation of Illinois Filed Aug. ,17,1959, Ser. No. 834,063 v1S Claims. (Q1. 340-213) This invention relatesto annunciator systems of the type wherein a visual alarm unit, such asa light unit, is provided for each variable to be monitored, and, whenthe variable becomes abnormal, a pair of eld contacts are actuated tooperate the visual alarm unit which indicates that the variable involvedhas just become abnormal. A manually operable acknowledgement switch isusually provided, which, when operated, changes the indication of thevisual alarm unit to indicate that the alarm has been acknowledged bythe operator. Usually, an audible alarm is also included to attract theoperators attention to a central control panel containing the visualalarm units `associated with practically all of the variables to bemonitored in the plant involved, so that the operator can determine at aglance the condition of all of the variables.

For the most part, annunciator systems of the lo'nd just described haveheretofore been hydraulically or relay controlled systems, and thesesystems left much to be desired from the standpoint of reliabilitybecause of mechanical wear and, in the case of the relays, additionallybecause the relay coils sometimes burned out. Obviously, it is quiteimportant for annunciator systems to be reliable, since otherwise, theycould not fulfill their intended purpose. More recently, static controlelements, such as magnetic cores, have been used in annunciator systemsto replace relays to provide a system of improved reliability.Annunciator systems have also been recently developed operating withtransistor control elements. Although these systems have provensatisfactory for some purposes, they are not as reliable as magneticcore annunciator systems and also do not have Suicient ilexibility to beuseful for certain applications, such as applications requiring a singlelight for each variable which `light flashes during initial alarmindication and is steady-on when acknowledged. Particularly withmagnetic core systems, the annunciators have not been provided with atrue manual reset feature. For true manual reset, an acknowledged alarmindication is removed by momentary depression of a manual reset switchprovided the variable has returned to normal. Heretofore, in annunciatorsystems using magnetic core elements, the depression of the manual resetswitch rwhen the variable was still abnormal changes a steadyacknowledged visual alarm indication to a ashing alarm indication,requiring depression of a manual acknowledgement switch to restore thesteady acknowledgement indication.

It is, accordingly, an object of the present invention to provide anannunciator system made of static elements, preferably magnetic coreelements, which have a higher degree of flexibility and, for certainapplications, are more simple and reliable than static annunciatorsystems heretofore developed.

Another object of the present invention is to provide an annunciatorsystem which includes one or more bistable control units, commonlyreferred to as flip-flop circuits, which ,are arranged and related toone another and to various control switches commonly found inannunciator systems in a unique manner so as to provide, in a relativelysimple, economical and reliable manner, a dashing light sequence withprovision for manual reset.

Still another object of the present invention is to CAQ lice

provide an annunciator system using static control elle.- ments, mostpreferably magnetic core elements, wherein, Yin a Very simple andreliable manner, the aforesaid flashing sequence may be .obtained usingonly a single alarm lamp. rAn ancillary object of the present inventionis to provide an annunciator system as just described wherein provisionis made for true manual reset operation.

Another object of the invention is t-o provide an annunciator system.satisfying any one or more ,of the above objects wherein operation witheither normallyopen or normally-closed signal contacts may be simplyobtained by the same equipment.

Still another object of the invention is to provide an annunciatorsystem providing a dim light condition indicating a normal condition ofthe variable in a unique manner using a magnetic amplifier.

In accordance with one aspect of the invention, there is associated witheach Variable to be monitored by the annunciator system two bistable orflip-flop circuits formed of static elements, preferably magnetic coreelements, which control the condition of operation of an associatedalarm light. Each bistable control circuit has two conditions ofoperation, one which will be referred to as a normal or initialcondition of operation and the other which will be referred to as anabnormal condition of operation. The normal and abnormal conditions ofeach variable are sensed by a primary detecting .element, commonly adevice including a set of normallyopen or normally-closed signalcontacts which are respectively opened or closed when the variable isnormal. The signal contacts are connected between la signal source,which may be a source of direct current potential, and an input to afirst one of said bistable control circuits. Operation of the signalcontacts into a position indicating an abnormal variable couples saidsignal source to the rst bistable control circuit to trigger it from aninitial or normal condition to an l.abnormal condition. The secondbistable control circuit is unaffected by the triggering of the firstbistable control circuit to an abnormal condition of operation. Forreasons to be explained, the bistable circuits are interconnected sothat the second bistable circuit will automatically be triggered intoits normal condition when the first bistable control circuit istriggered into its normal condition. Means are provided for flashing analarm light when the fir-st bistable control circuit is triggered intoits abnormal condition. Most preferably, the first bistable controlcircuit controls the operation of a gate through which a source ofenergizing potential is coupled to the alarm light or to an intermediatecontrol device such as a magnetic amplilier. A flashing indication isprovided preferably by opening and closing the gate at a visible ashingrate as long as the first bistable control circuit is in its abnormalcondition and the second bistable circuit remains in its normalcondition.

A manually operable acknowledgement switch is provided which, uponmomentary operation thereof, feeds a control signal to an input of thesecond bistable corn trol circuit to trigger it from its normal to itsabnormal condition. Means are provided which couple a continuousenergizing potential to the alarm light or to an intermediate controldevice associated therewith lto operate the alarm light in a steady-oncondition when the second bistable control circuit is in its abnormalcondition. Most advantageously, the pulsating or flashing signal at theoutput of the aforementioned gate is mixed with a continuous energizingsignal controlled lby the second bistable control circuit producing anoverall result which is a steady light indication. This mixing ofsignals is particularly desirable where an intermediate control devicecontrols the operation of the alarm light, the control device acting asan on or an off switch, such as in the case of a magnetic amplifierhaving saturated and unsaturated conditions of operation.

A manually operable reset switch is most advantageously provided,momentary operation of the manual reset switch normally connecting asignal to an input of the first bistable control circuit which returnsthe same to its normal condition provided the associated variableresponsive signal contacts are then in their normal condition indicatingstate. Otherwise, the first-mentioned signal source coupled through thesignal contacts will maintain the first bistable control circuit in itstabnormal condition despite the feeding of a reset signal thereto. Aspreviously indicated, when the first bistable control circuit istriggered into its normal condition, the second bistable control circuitalso returns to its normal condition. When both bistable controlcircuits are in their normal condition, the alarm light is de-energizeddue to the resultant de-coupling of the aforesaid energizing signalsfrom the alarm light or the intermediate control device controlling thesame.

In accordance with another aspect of the invention, the aforesaidintermediate control device to which the aforementioned energizingsignals lare fed comprises a special type of magnetic Iamplifier.Instead of using a high-quality, magnetic core material having a llowleakage current in the output winding thereof, the magnetic amplifieruses a relatively low quality iron in the core thereof which may be acommercial gradesilicon iron material, to provide a relatively highleakage current in the output winding, so that an alarm light connectedin series with the output winding and a source of 60 cycle AiC. voltagewill be operated in a dim but visible condition when the core is in anunsaturated state.

The aforementioned energizing signals `are fed in parallel to theprimary winding of the magnetic amplifier, which signals saturate thecore material. The alarm light connected in series with the outputwinding of the magnetic amplifier receives a relatively high energizingcurrent when the core of the magnetic amplifier is saturated.

In accordance with still another aspect of the invention, in addition tothe alarm flight lcircuit above described, a second alarm light may beassociated with each variable which alarm light provides a steady-onlight indication only when the Yassociated signal contacts are in theirabnormal indicating state. The second lalarm light may be mounted behinda translucent panel adjacent the first mentioned alarm light so that an-apparent single light indication is provided which is the resultant ofthe two alarm lights. This application has the advantage of increasedreliability since failure of the first mentioned alarm light will stillleave a visual light indication. A steady-on light of the second alarmlight superimposed on the fi-ashing light of the first-mentioned alarmlight will result in an overall flashing light indication, `so that thesecond alarm light will not adversely affect the flashing light sequencedesired.

Another aspect of the invention relates to the lighting of thesecond-mentioned alarm iight through a magnetic amplifier whose inputcircuit includes provision for connection to either normally-open ornormally-closed signal contacts. The use of normally-closed signalcontacts to shunt current around the alarm light generally requires acurrent-limiting resistor in `series with the fvariable responsivesignal contacts to prevent a short circuit condition. Where a highwattage light is desired, this arrangement is disadvantageous becausethe resistor must take the large current passing through the light,resulting in wastage of power, and, in many cases, problems inpreventing overheating of the adjacent equipment.

In accordance with the present invention, the normallyclosed signalcontacts are connected in parallel with the input windings of a magneticamplifier which greatly redu-ces the current requirements of the inputcircuit. In such case, the normally-closed signal contacts shunt theprimary windings of the magnetic amplifier. Opening of these contactscauses a saturating current to flow in the primary windings whichresults in the passage of a large energizing current in the outputwinding of the magnetic amplifier. This magnetic amplifier circuit isalso readily adaptable for use in normally-open signal contacts whichare connected in series with the input windings of the magneticamplifier.

Other aspects of the invention relate to the detailsy of the bistablecontrol circuits and the specific interconnections of various componentsassociated therewith. These together with the various aforesaid aspectsof the invention will be described in `detail in the specification tofollow, the claims and the drawings wherein:

FIG. l is a simplified box diagram of a preferred form of the presentinvention;

FIG. 2 is a schematic diagram of the preferred embodiment of the form ofthe invention illustrated in FIG. l;

FIG. 3 shows a modified form of the invention wherein ya magneticamplifier is associated with the signal contacts which may be eithernormally-open or normally-closed; and

FIG. 4 shows the B-H curve of the magnetic core material used in themagnetic amplifiers illustrated in FIGS. l through 3.

Referring now to FIG. 1,'an annunciator system is there shown includinga number of annunciator units or stations 2 connected in parallelbetween various buses 4 through 11 which will be identified in theparagraphs to follow. Each of the annunciator stations contains all ofthe components exclusively associated with each variable to fbemonitored and includes visual alarm means 14 which may include `anincandescent lamp 16 mounted behind a lense unit (not shown) or `atranslucent panel 17. -For reasons to be explained, a secondincandescent lamp 16 is also preferably mounted behind the panel 17 butit could be omitted Without yaffecting the light sequence provided bythe annunciator system.

Audible alarm means 18 including a horn or bell 20 is used in commonwith all of the vannunciator stations and, in conjunction with thelalarm lamp 16 and/ or 16', provides various signals to indicate thenormal, initial albnormal and acknowledged abnormal conditions of theassociated variables.

The operation of the horn 2@ and the various lights 16 and 16' arecontrolled by variable responsive means associated with ea-channunciator unit, the Ivariable responsive means shown in the drawingsbeing either normally-open signal contacts 24 or normally-closed signalcontacts 26. A common manually operable acknowledgement pushbuttonswitch 28 and a common manually operable pushbutton reset switch 8f) areprovided for manually controlling the annunciator system. Various meansto be described interconnect the buses 4 through 11, the individualsignal contacts 24 or 26, the lamps 16 and 16', the common horn 20 andthe switches 28 and 30, to form an operative annunciator system. As willappear, these means are adapted to vsound the horn 2f) and cause afiashing indication to appear on the alarm light 16 associ-ated with anyvariable which becomes abnormal upon closure of the associatednormally-open signal contacts 24 or the opening of the associatednormally-'closed signal contacts 26. Upon momentary depression of themanually operable acknowledgement switch 28, the flashing indication onalarm lamp 16 is changed to a steady-on condition, and the horn 26 issilenced. The steady-on condition of the alarm lamp 16 will continueuntil the variable involved has returned to normal and the reset switch30 subsequently is momentarily depressed. When these conditions are met,the alarm =lamp 16 will become deenergized.

The alarm lamp 16 is provided with each annunciator station in theinterest of increasing the reliability of the annunciator system. Eachlamp 16 responds directly to the associated signal contacts 24 or 26 soas to provide spaanse a steady-on light condition when the associatedvariable is abnormal or a de-energized condition when the variable isnormal.

The alarm lamp 16 is preferably mounted behind the same translucentpanel 17 as the alarm lamp 16, so th-at an over-all single lightindication is provided which is a flashing indication during an initialalarm condition and a steady-on condition after acknowledgement. Thepurpose of the alarm light 16 is to provide an alarm indication shouldthe alarm light 16 burn out or otherwise become inoperable.

For controlling the operation of the alarm lamps 16, each lannunciatorstation is provided with a pair of rbistable control circuits generallyindicated by reference numerals 32 and 34. Bistable control circuit 32includes a pair of static current control devices 32a and 32h andbistable control circuit 34 includes a pair of static control devices34a `and 34h. In accordance with the broadest aspect of the invention,the current control devices may be any kind of static element such astransistor or magnetic core elements, magnetic cores being the preferredtype of static element, however, for reasons including theirreliability, `and the simplicity of the circuitry resulting from theiruse. Eachv pair of current control devices are connected to form abistable or flip-flop circuit preferably of the type where the deviceshave opposite stable conductive or signal output conditions which arereversed when the conductive or output conditions of one device ischanged.

The static devices 32a and 34a of bistable control circuits 32 and 34respectively have outputs 36 and 37 connected to inputs 3S and 39respectively of the associated static devices 32b and 341). Likewise,the static devices 32h 'and 341; have outputs 40 yand 41 respectivelyconnected to inputs 41 and 42 of static devices 32a and 34a. For reasonsto be explained, output 36 of static device 32a of bistable controlcircuit 32 is connected by a conductor 44 to the input 39 of the stat-icdevice 34h of the other bistable control circuit 34.

The two possible operating states of the bistable control circuitsconsidered as a whole will be respectively referred to as the normal andabnormal states thereof. The connection between the output 36 of thestatic device '32a and the input 39 of the static device 34b is suchthat the change in the output condition of the static device 32a whenthe bistable circuit 32 is `changed from its abnormal to its normaloperating state will trigger the bistable control circuit 34 from anabnormal to 'a normal operating state. However, the output conditionexisting at output 36 of static device 32a when the bistable controlcircuit 32 changes from its normal to its abnormal operating state willnot have any eect upon the bistable control circuit 34. This arrangementof bistable control circuits provides a relatively simple and reliablemeans for controlling the operation of the associated lalarm light 16 inresponse to the various operations of the associated signal contacts 24and 26 `and the acknowledgement Yand reset switches 28 and 3i).

A pair of screw terminals 44--44 lare provided in e-ach annunciator unit2 `across which the normally-open signal contacts 24 may be removablyconnected. Provision is also made for shorting the terminals 44-44 whenthe normmly-closed signal contacts 26 yare utilized. To this end, ajumper may be used, or, -as illustrated, a single pole double-throwswitch 46 is provided with the movable pole thereof connected to thelower terminal 44 and movaible selectively against an N.C. switchcontact 48 connected to the upper terminal 44 or an unconnected N.O.switch Contact 501. The upper terminal 44 is connected by aconductor 52to the bus 5, sometimes referred to as a signal bus. The signal bus 5 isshown connected to the terminal of a source 53 of direct currentvoltage, but, in accordance with the broader aspects of the invention,could be a source of pulses. The lower terminal 44 is connected througha current-limiting resistor 54 to the upper of a pair of screw terminals56-56 across which the set of normally-closed signal contacts 26 may beconnected when operation with this type of field contacts is desired.The alarm lamp 16 is connected across the terminals 56-56. The lowerterminal 56 is connected by a conductor 58, tothe lbus 8, referred to asa common bus, which is grounded. A conductor 6i) extends between thejuncture of current-limiting resistor 54 and the upper terminal 56 andthe input 41 of the static device 32a of the bistable control circuit32.

The bistable control circuit 32 is 4arranged so that it will betriggered from its normal operating state to its abnormal operatingstate whenever the signal on the signal bus 5 is connected to the input41. For oper-ation with the normally-open signal contacts 24, thisresults upon closure of the signal contacts ywhich connects the signalbus 5 through these contacts, current-limiting resistor 54 and conductor60 to the input 41 of the [bistable control circuit. The same resultoccurs with operation with the normally-closed signal contacts 26. Insuch case, the input 41 is continuously connected to the signal bus 5through the resistor S4, the switch 46 and conductor 52. When theassociated variable is normal, the signal from the bus 5 is shortcircuited to ground by the normallyclosed signal contacts 26. Opening ofthese contacts will, however, result in the coupling of the signal onthe bus 5 to the bistable control circuit input 41 which triggers thebistable control circuit 32 into its abnormal operating state. Thisstate is maintained until externally triggered into its normal operatingstate. However, the bistable control circuit 32 cannot be triggered intothe latter state until the input 41 is uncoupled from the signal bus 5,as by the opening ofthe normally-open signal contacts 24 or the closingof normallyJclosed signal contacts 26.

When the bistable control circuit 32 is in its abnormal operating stateand the other bistable control unit 34 is in its normal operating state,the visual alarm lamp` 16 provides an initial alarm indication which, inthe embodiment of the invention illustrated, is a flashing indication.Also, the horn 2t) will be sounded.

The circuit for providing a flashing indication on the alarm lamp 16 inthe embodiment illustrated in FIG. 1 includes a gate unit 64 having acontrol signal input teruninal 66, a signal input terminal 68 and agated signal `output terminal 70. The signal input terminal 68 isconnected by a conductor 72 to a signal bus 11 extending to a signalsource 74. The gated signal output terminal 70 is connected by aconductor 76 to the input of visual alarm means 14. When the gate unit64 is open, energizing signals from the sign-al source 74 pass throughthe gate unit to the input of the visual alarm means 14. When the gateunit 64 is closed, the energizing signals do not pass through the gatecontrol unit 64.

The input 66 of the gate unit 64 extends through an isolating diode 78to the output 36 of the static device 32a of the bistable controlcircuit 32 and also through an isolating diode 80 to asher bus 6 whichis connected to a source of signals 82 which provides a signal at theinput terminal 66 of the gate control unit 64 which, in the absence ofother gate-closing signals thereat will open and close the gate unit 64at a visible hashing rate. When the bistable control circuit 32 is inits normal operating state, a gate-closing signal is fed from the outputthereof to the input terminal of the gate unit 64 which continuouslycloses the gate unit. When the bistable control circuit 32 is in itsabnormal operating state, the only operative signal fed to the gateinput terminal 66 is from the ilasher bus 6 which, as above indicated,alternately opens and closes the gate unit at a visible flashing rate soas to feed a modulated energizing signal to visual alarm means 14 whichlproduces a flashing indication on the alarm lamp 16.

A circuit for sounding the horn 2) is established by an annunciatorstation when `the associated variable initially becomes abnormal. Thiscircuit extends from the conductor 60 extending from the bottom terminalof the current-limiting resistor 54, and includes in the case where thesignal bus is connected to a source of direct current potential apulsing circuit S1 and an isolating diode 83 connected by a conductor 82to horn bus 4. The horn bus 4 extends to the input 84 of a horn bistablecontrol circuit 86 which may be similar to either the bistable controlcircuit 32 or 34. When the direct current potential on the signal bus 5is connected to the pulse circuit 81, a pulse is produced of a polaritywhich triggers the bistable control circuit 86 into an operating statewhich provides an output condition at its output terminal 88 capable ofenergizing audible alarm means 18 to which it is connected to sound thehorn 20.

In addition to the ashing of alarm lamp 16 and the sounding of the horn2t) upon an initial abnormal condition of a variable, the alarm lamp 16connected between common bus 8 and the lower end of the current-limitingresistor 54 will be energized by the voltage connected thereto fromsignal bus 5 upon closure of the normallyopen signal contacts 24 or theopening of the norma1ly closed signal contacts 26 which previously shortcircuited the lamp 16. Where the alarm lamps 16 and 16 are mountedbehind the aforesaid common translucent panel 17, the overall indicationwill still be a ashing light. As previously explained, the purpose ofthe lamp 16 is merely to provide some kind of light indication shouldalarm lamp 16 burn out or be inoperative because of a defect in thecontrol circuit therefor.

As previously indicated, momentary closure of the acknowledgementpushbutton switch 28 will change the light indication on the translucentpanel 17 from a Hashing indication to a steady-on indication and soundthe horn 2t). To this end, the acknowledgement switch 28 is connectedbetween the upper terminal of direct current voltage source 53 or othersuitable signal source and acknowledgement bus 9 and the bus 9 isconnected by a conductor 9i) to the input 42 of the bistable controlcircuit 34 of each annunciator station. The momentary closure of theswitch 23 will couple a signal voltage capable of triggering thebistable control circuit 34 from its normal operating state to itsabnormal indicating state, provided the associated bistable controlcircuit 32 is also in its abnormal operating state. It it were in itsnormal operating state, the condition at the output 36 of the staticdevice 32a thereof is such that the signal coupled to the input 39 ofthe static device 3412 will keep the bistable control circuit 34 in itsnormal operating state. When the bistable control circuit 34 istriggered into its abnormal operating state by operation ofacknowledgement switch 28, a signal is fed to the input of the visualalarm means 14 which will result in a continuous indication on the alarmlamp 16.

In the embodiment of the invention illustrated in FIG. l, the staticdevice 34h of each bistable control circuit 34 acts as a gate for gatingthe signal from signal bus 11. A conductor 92 extends from the signalbus 11 to a signal input terminal 94 of each device 34h. The signalappearing therein is coupled through the static device 34]) to theoutput terminal 43 thereof when the bistable control circuit 34 is inits abnormal operating state. This signal, which is a continuous signal,is fed through a conductor 96 to the input of visual alarm means 14.

In the circuit just described, it will be apparent that two signals arefed in parallel to the input of the visual alarm means 14, one amodulated signal fed by a conductor 76 from the gate unit 64 and theother a continuous signal fed from device 3417 acting as a gate. Thevisual alarm means 14 is designed so that the combination of acontinuous signal and a signal modulated at a visible flashing rate willproduce a continuous indication on the alarm lamp 16. It will bedescribed in connection with the specific and preferred annunciatorcircuit illustrated in FIG. 2.

For silencing the horn 2t) after acknowledgement, a

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conductor 98 extends from acknowledgement bus 9 to an input lili) of thehorn bistable control circuit 86 which triggers the circuit into itsnormal operating state. This results in an output condition at theoutput 88 thereof which will result in the de-energization of the horn20.

After acknowledgement, the steady-on light indication on any alarm lamp16 is locked-in until momentary operation of the reset pushbutton switchSti. Operation of this switch will de-energize the alarm lamp 16provided the signal contacts have been returned to their normal indi@cation position. The reset switch 311 is connected between the upperterminal of the direct current voltage source 53 and reset bus 1l). Aconductor 162 extends between the reset bus 1@ and the input 38 of thestatic device 32h of the bistable control circuit 32 of each annunciatorstation. Momentary closure of the reset switch 30 will couple a Voltageof proper polarity to the input 3S of any static device 32b in anabnormal state or condition of operation which will trigger the bistablecontrol circuit involved into its normal operating state, provided theassociated signal contacts have been returned to their normal indicatingstate. Otherwise, operation or the reset switch 30 will have no result.When the bistable control circuit 32 is returned to its normal operatingstate, as previously indicated, the signal condition at the output 36 ofthe associated static device 32a will be effective to trigger theassociated bistable control circuit 34 to its normal operating state.This will close the associated gate unit 64 and the gate formed by thestatic device 34h, resulting in the de-energization of the alarm lamp16. The alarm lamp 16 has then already been de-energized Iwhen theassociated signal contacts returned to their normal indieating position.

Refer now more particularly to FIG. 2 -which shows a substantiallycomplete circuit diagram for the annunciator circuit illustrated in boxform in FIG. l constructed with magnetic core static elements. Only oneof the annunciator stations 2 appears in this figure, it beingunderstood that all of the other annunciator stations are identical tothe one illustrated. Cor-responding reference numerals have been used toidentify corresponding portions of the circuit in FIGS. l and 2. All ofthe bistable control circuits in the embodiment of FIG. 2 may beconventional bistable magnetic core circuits. Bistable control circuit32 comprises a pair of magnetic core units 32a and 32b each of which maycomprise a core 32a-1 or 32h-1 made of a magnetic material having arectangular hysteresis curve. An input winding 32a-2 or 32h-2 and anoutput winding 32a-3 or 6211-3 having a greater number of windings thanthe associated input winding is Wound around each core. A resistor 104is connected between the upper terminal of the input winding 32a-2 andthe input 41 to the bistable control circuit 32 involved. The bottomterminal of the input winding 32a-2 is connected to a ground conductor166 extending to ground bus 8. The upper terminal of the output winding32a-3 may constitute the output 36 referred to in FIG. l and isconnected through a diode 168 polarized to pass only positive pulses toa resistor connected to the upper terminal of the input Winding B2b-2 ofthe magnetic core unit 321;. The bottom terminal of the input winding32h-2 is connected by a conductor i112 to grounded conductor 166. Theupper terminal of the output winding 3'2b-3 of the magnetic core unit32h is connected to a conductor 113 leading to a diode 114 polarized topass only positive pulses to the input 41 of the magnetic core unit 32d.The bottom terminal of the output winding 32h-3 is connected by aconductor 115 to signal bus 11 to which is coupled a source ofalternating current -which may be a signal from an output 116 of a 17kc. signal source 74.. The signal source 74 has a second output 118coupled to a signal bus 120# which does not appear in the embodiment ofFIG. l, the signal appearing at the output 118` also being a 17 kc.signal but one 180 out of phase with the signal at output 116. The lbus129 is connected via a conductor 121 at each annunciator station to thebottom terminal of the output winding 32a-3 of the associated magneticcore unit 32a.

The aforesaid coupling conductor 44 extends from the upper terminal ofthe output winding 32a-3 through a diode 124 polarized to pass onlypositive pulses to the right hand end of a diode S in the magnetic corebistable control circuit 34 which diode 108 corresponds to the diode 168in the bistable control circuit 32. The details of the magnetic corebistable control circuit 34 and the horn bistable control circuit 86 maybe identical to bistable control circuit 32 just described, so that adetailed description of these control circuits will not be given. EX-cept for the magnetic core elements which are identied by referencenumbers 34a--34b, 86a-86b, corresponding elements of these Abistablecontrol circuits are similarly numbered except that a single prime willbe used in association with the reference numbers of the bistablecontrol circuit 34 and a double prime will be used in association withthe reference numbers in the bistable control circuit 36. Suice it tosay this point that the 17 kc. signal on bus 1i. is fed by conductors11S and 115 to the bottom terminals of the output windings of the righthand magnetic core units 34h and 865, respectively, and the 180 out ofphase 17 lic. `signal on bus 12d is fed by conductors 121. and 121" tothe bottom terminals of the left hand magnetic core units 34a and 86a.

Each of the magnetic core unit-s 32a, 321), 34a, 34b, 86a and @6b of thevarious bistable control circuits 32, 34 and 86 is connected as a notgate circuit which provides at the upper terminal of the associatedoutput winding, to be referred to as a signal output terminal,relatively large positive pulses indicating the opening of the gatecircuit involved provided the upper terminal of the associated inputwinding did not receive a similar positive pulse onehalf cycle before.The associated signal input terminal, such as terminal 41 of core unit132:1, is referred to as a not control lsignal input terminal. Theappearance of such large positive pulses is referred to as a signaloutput condition. Conversely, relatively small insignificant positivepulses will appear at the upper terminal of the associated outputWinding when a similar positive pulse was fed to the associated inputwinding one-half cycle before. Such insigniiicant pulses is referred toas a no-signal output condition. This action is due to the factors nowto be described.

As previously indicated, due to the aforesaid diodes associated with thebistable control circuits, only positive voltage pulses appearing on thebuses 1=1 and 120 are effective to provide operating current through'the windings of the core units and these positive pulses are applied180 out of phase respectively to the bottom terminals of the outputwindings of the associated cores of each bistable control circuit.Considering a particular magnetic core, if the current flowing in theoutput winding as a result of such a positive pulse is in a directionwhich will maintain the existing state of saturation of the core, thenthe output winding acts as a relatively low impedance so that arelatively large current pulsation results. If, on the other hand, thecore is in a `state of saturation such that the current resulting fromthe positive voltage ,pulse would drive the core to an opposite statelof operation, then the core acts as a relatively high impedance andonly a relatively small current pulsation results. In the formersituation, the gate said to be open since large current pulsations arefed through the core and in the latter case the gate is said to beclosed since relatively small or current pulsations pass through thecore.

With the yinterconnection of the magnetic cores described, where the`output of each core unit is coupled to the input of the associated coreunit, a .signal output condition of a particular core will maintain arelatively nosignal output condition in the other core and vice versa toform a true bistable circuit. Thus, if a continuous or momentarypositive voltage .is fed to the not control sigl@ nal input terminal ofa core unit having a signal output condition, this voltage will resultin a nosignal output condition of the core unit which will then effect asignal output condition in the associated core unit which results in thetriggering of the bistable control circuit involved into an oppositeoperating state.

When a particular annunciator station has been reset and the associatedsignal contacts are in their normal indicating position, the magneticcore bistable units 32 and 34 will be in a condition whereby theright-hand magnetic cores will be in a no-signal output condition andthe lefthand core will be i-n a signal output condition. Relativelylarge positive current pulsations will then be passing through theoutput winding 32a-3 of the magnetic core unit 32a of the annunciatorstation involved. Part of this current will flow through the diode 103,resistor 1101 and the input winding 32h-2 of magnetic core unit 32h andpart of this current will pass through diode 78 (polarized to pass onlypositive current pulsations) to the aforesaid gate unit 64. The gateunit 64 in FIG. 2 is a not magnetic core gate circuit similar to the notmagnetic core gate circuits making up bistable control circuits 32, 34and S6. rl`hus it has an input winding 64a-2, an output winding erta-3having many more windings than the input winding and a core 64a-1 aroundwhich these windings extend. The upper end of the input winding 6441-2is connected to a resistor 127 which, in turn, is connected to thejuncture between diode 78 and the aforesaid diode 80 connected to theflasher bus 6. The bottom terminal of the input winding 64a-2 is coupledby a conductor 129 to .ground conductor 166 leading to the ground bus 8.The upper terminal of the output winding 62a-3 is connected through anisolating diode 131 polarized to pass positive current pulsations to theconductor 7 6 leading to the visual alarm means generally indicated byreference numeral 14, and which will be described in detail in theparagraphs to follow. The bottom terminal of the output winding 64-3 isconnected to the aforesaid conductor i` leading to the 17 kc. signal bus11. The positive current pulses fed to the input Winding 6401-2 of themagnetic core unit 64 from .magnetic'core unit 32a are 180 out of phasewith the positive current pulses fed to the output winding 6441-3 frombus 1-1.

The output winding 64a--3` presents a relatively large impedance to flowof positive current pulses therethrough to provide a closed condition ofthe gate .if the positive current pulses fed to the output Winding areoperative to switch the state of saturation of the associated core64a-1. This occurs when the input winding 64a-2 has received arelatively large positive current pulse one-half cycle before which setsthe core 64a-1 `into a reference state of saturation. As `previouslyindicated, such current pulses are present -in the input winding 64a-2when the bistable cont-rol circuit 32 is in its normal operating state,where the output of the left-hand core unit 32a has a signal outputcondition. Following the triggering of bistable control circuit 32 intoits abnormal operating state upon the operation of the associated signalcontacts 24 or '26 to their abnormal variable indicating position, theoutput of the magnetic core unit 32a vhas a no-signaloutput condition sothat the core 64a-1 is not resetto its reference state of saturation.Consequently, the current pulses passing -through the output winding64a-3 ofthe gate unit 64 will be operative to maintain the saturation ofthe core .as long as this condition prevails. In this situation, theoutput winding '64M-3 has a relatively low impedance to the passage ofpositive current pulses. However, as previously explained, positivecurrent pulses are fed tothe input winding A64rz-2 from the :flasher bus 6 periodically at a visible flashing rate, so that a gate unit 64 isalternately opened and closed at a visible ashing rate when the bistablekcontrol circuit 32 is in its abnormal indicating state. This conditionof the gate unit 64 continues until the rannunciator circuit is reset.

As previously indicated, the dashing signal received from the gate unit64 is superimposed within the visual alarm means 14 upon a signal fedfrom the right-hand magnetic core unit 34b of the bistable controlci-rcuit 34. The right-hand magnetic core unit 34b acts as an open gatecircuit after it has been acknowledged. Normally, the right-handmagnetic core unit 34b is in a no-signal output condition, which meansthat the output of the left-hand magnetic core unit 34a which feeds theinput Winding of magnetic core unit 34h is in a signal output condition.When 4the acknowledgement pushbutton switch 28 is momentarily closed,this feeds a positive pulse via conductor 90 and a diode 134 polarizedto pass positive pulses to the input winding 34a-2 of the magnetic coreunit 34a. Momentary closure of the acknowledgement `switch 28 will feeda relatively large positive pulse to the not signal input terminal ofthe left-hand magnetic core unit 34a to trigger the same into ano-signal output condition which, in turn, triggers the right-hand coreunit 3417 into a signal output condition. The resultant large positivecurrent pulses passing through the output winding 3a4b-3l of themagnetic core unit 341) passes, in part, through diode '136 pola-rizedto pass only positive pulses to the input of visual alarm means 14. Acontinuous series of such positive current pulses passes through theinput of visual alarm means 14 to effect a steady-on condition of theassociated alarm lamp 16 until the bistable control circuit 34 isreturned to it-s normal operating state. As previously indicated, thisoccurs when the signal contacts 24 or 26 involved are returned to theirnormal variable indicating position and reset lbushbutton switch 30 issubsequently momentarily depressed. Then, a positive pulse is fed fromreset bus 9 through conductor 102 and a diode 140 at each annunciatorstation, the diode being polarized to pass only positive pulses to theinput winding 3217-2 of the righthand magnetic core unit 32b of thebistable control circuit 32. r1`his changes the signal output conditionof the magnetic core -unit 3211 to a no-signal output condition which,in turn, effects the change of the output condition of the left-handmagnetic core unit 32a from a no-signal output condition to a signaloutput condition which effects the closing of the gate unit 64. Also,the resultant positive pulses in the output circuit of the magnetic coreunit 32a are coupled through the conductor 44 and the diode 124 totrigger the bistable control circuit 34 into its normal operating stateby changing the signal output condition of the magnetic core unit 34b toa no-signal output condition.

As previously indicated, the visual alarm means 14 is designed toprovide a flashing indication on the alarm lamp 16 provided only asignal modulated at a visible ashing rate is fed to the input thereof,and to provide a steady-on light indication thereon when a substantiallycontinuous constant amplitude signal is fed thereto. To this end, a pairof magnetic amplifiers 142111 and 14211 are provided. Magnetic amplifier142e has an input winding 14211-1 and an output winding 14211-2 andmagnetic amplier 1421) has an input winding 1421)-1 and an outputwinding 142b-2. For reasons to be explained, the input windings 14211-1and 14211-1 are connected in series bucking relation so that any A C.potential induced therein from the output windings 14211-2 and 14211-2will cancel out. The output windings 142a-2 and 1421 -2 are connected inseries with the alarm lamp 16'and with a source of alternating currentof ordinary commercial 60 cycle frequency through the medium of buses144-146. The aforesaid conductors 76 and 96 extending from the signaloutput terminals of gate units 64 and 3412 extend to the upper end ofthe input winding 14211-1. The bottom end of the input winding 142b-1 isconnected by a conductor 14S to the ground bus 8. The magnetic coreamplifiers 142,11 and 14211 act as saturable devices where the outputwindings 14211-2 and 14217-2 act as relatively low impedances to flow of60 cycle alternating current when the associated cores are saturated,and act as relatively high impedances when the associated cores areunsaturated.

12 In the latter case, little or no current flows through the alarm lamp16 and in the former case a relatively high current flows through thealarm lamp 16 to light the same brightly.

The flow of relatively large positive cur-rent pulses from either thegate unit 64a or the gate unit 341; through the input windings 114211-1and 1421;-1 will saturate the associated cores to energize the alarmlamp 16. When current pulses flowing in the input windings originateonly from the gate 64a, which is alternately opened and closed at avisible flashing rate, the alarm lamp 16 will accordingly Hash at avisible flashing rate. When the gate 34b is open to pass continuouspositive pulses to the input winding 14211-1 and 142b-1, then the coresare substantially continuously saturated so that a Steady-on lightappears on the alarm lamp 16.

A filter capacitor 149 may be connected in parallel with the inputwindings 14211-11 and 14217-1 to lter the 17 kc. pulse components fromthe current fed thereto so that a substantially direct current potentialis applied to the input windings. ciently small value that it does notlter out the lower frequency modulations of the 17 kc. current pulseswhich effect flashing of the alarm lamp 16.

The yaudible alarm means 18 includes, in addition to the horn Ztl, lapair of magnetic lamplifiers 15211 and 152b which may be identical toand operated in the same manner as the magnetic amplifiers 142m! and14211 just described. Thus, these magnetic ampliers have input windings1752a-1 and 15211-1 connected in series bucking relation and outputwindings 152a-2 and 15211-2 connected in series with the horn 20 andwith the 60 cycle alternating current buses 144 and 146. The upper endof the input winding of magnetic amplifier 15201 is connected through adiode 154 polarized to pass only positive pulses to the signal outputterminal 156 of magnetic core bistable control circuit $6, the terminal156 being connected to the upper end of the output winding 8611-3 of theright-hand magnetic core unit 8611 thereof. A lter capacitor 157 isconnected in parallel with input windings 15211-1 and 152b-1 of magneticampliers 15211 and 15217 to lter out the 17 k.c. pulses. It is apparentthat the horn 20 will be sounded Whenever :the right-hand magnetic coreunit 86h is in a signal output condition and will be silenced wheneverthe right-hand magnetic core 86h is in a relatively nosignal outputcondition.

The pulse circuit $1 at each `annunciator station for pulsing the hornbus 4 may comprise Va capacitor connected between diode 83 and the inputline 60` so that a positive pulse is produced as capacitor 6i) chargesup to the direct -cunrent voltage coupled thereto by the operation ofthe signal contacts 24 or 26 to their abnormal vari-able indicatingcondition.

Means are provided in the annunciator circuit shown for manuallytriggering al1 of the rannunciator stations simultaneously to test theoperation of the system. To this end, a test busl 153 is provided whichis connected through a normally-open pushbu-tton switch 161)` to thepositive terminal of the direct current voltage source 53. A conductor161 is associated with each annunciator station which extends from thetest bus 158 through a diode 162 polarized to pass a positive voltage tothe input 41 of the associated bistable `control circuit 32. Moment-aryclosure of the test pushbutton switch 160 will trigger the bistablecontrol circuits 32 into their abnormal operating state which providesflashing indications on the alarm lamps 16. Subsequent operation ofacknowledgement pushbutton switch 128 will change the flashingindications on alarm lamps 16 to a steady-on indication, and subsequentdepression of the reset pushbutton switch 30 will reset all theyannunciator stations.

The customer may desire to have a dimly lit indication on the alarmlamps 16 so that the operating condition of the alarm lamps 16 can heimmediately determined by noting the dim light indications thereof. Tothis end,

However, the capacitor 149 is of sut1i.

in accordance with another aspect of the invention, unique means areprovided to obtain 4a dim indication on the alarm lamps 16. This isobtained in each of the visual a-larm means 14 by using a high loss,commercial grade iron in the cores of magnetic amplifiers 142a and 142b,such as a silicon-iron material, so that a relatively large leakagecurrent will tiow through the secondary windings 142a-Z and 14217-2during the unsaturated condition of the cores to light the associatedalarm lamps 116 dimly. FIG. 4 illustrates the hysteresis curve of a highloss commercial grade iron. Magnetic rcores in current use in controldevices use high grade ferrous materials having rectangular shapedhysteresis curves.

As previously described, Ithe alarm lamp 16 of each annunciator stationis placed in series with the currentlimi-ting resistor 54 where theannunciator system is adapted for use with normally-closed fieldcontacts 25 placed in shunt with the Ialarm lamp 16'. In order to insureoperation oi annunciator stations with normally-open signal contacts 24should the -alarm lamp 16 burn out, or to otherwise provide proper inputimpedance conditions, a resistor 163 may be placed in parallel with eachalarm lamp 16. In this circuit, appreciable current flows through thecurrent-limiting resistor, namely the current which is necessary toenergize the alarm lamp 16. The resistor 54 must accordingly besuiiiciently small Ito allow this required current to flow under thevoltage conditions involved. A relatively small resistor 54 will, ofcourse, result in appreciable current drain and consequent heating andpower loss under normal v-ariable conditions when normally-closed signalcontacts yare used. Since it is desirable -to minimize the amount ofcurrent passing through current-limiting resistor 54 to minimize powerloss and heating problems, the alarm lamp 16 is desirably a low wattagelamp. For example, the alarm lamp 16 may be a one watt lam-p whereas thealarm lamps 16 my preferbly be siX wa-tt lamps. To further reduce thecurrent drain required in the input circuit to the various annunciatorstations, the input `circuit shown in FIG. 3 is preferred.

This input circuit includes -a pair of magnetic amplifiers 16511 and16517 larranged in a manner similar to that previously described inconnection with the magnetic amplifiers associated with the alarm lamps16 and the horn 20. Thus, magnetic amplifier 165a has an input winding16511-1 and an output winding 165a-2 and the magnetic amplifier 165b hasan input winding 165b-1 and an output winding 165b-2. The input windings165a-1 and 165b-1 are connected in series bucking relationship. Theupper end of the input winding 165a-1 is connected in series with a muchlarger current-limiting resistor 54 than the resistor 54 previouslydescribed and the bottom end of the input winding 165b-1 is connected.to a lower terminal 44 of a pair of terminals `44---44 across which thenormally-open signal contacts 24 are connected. The upper terminal 44,as in the previously described circuit, is connected to the signal bus5.

Terminals 56-56 across which the normally-closed signal contacts 26 areto be placed are respectively connected between the juncture of resistor54' and the upper end of the input winding 16261-1, land the ground busS. The latter juncture point is connected by the aforesaid conductor 60to the input 41 of the bistable control circuit 32.

The output windings 16561-2 and 165b-2 are connected in series With oneanother and with the alarm lamp 16', which may now be a six wat-t lamp,Iand with the 60 cycle current buses 144 and 146. Where dim operation ofthe -alarm lamp 16 is desired, the cores of magnetic amplifiers 165a and165]; are made of a high loss material exemplitied by the hysteresiscurve in FIG. 4. v

The input circuit shown in FIG. 3 is designed so that upon closing ofnormally-open signal contacts 24 or opening of normally-closed signalcontacts 26 (in the latter situation the terminals 44-44 are shorted),the current iiowing through the resistor 54 is suicient to satura-te thecores ofthe magnetic amplifiers a and 165b. As is 'common knowledge inthe art, lthe `amount' of current required to saturate such magneticcores may be much less than the current required to light a one wattl-amp. The resistor 54', therefore, may be many times larger than theresistor 54 required in the prtviously described circuit so that currentflow under both normal and `abnormal variable conditions issubstantially less than before. When the cores of the magneticamplifiers are saturated, the impedance of the output windings 165a-2and 165b-2 is relatively low, so that relatively large current owsthrough the alarm lamp 16 to light the same brightly. When `the cores`are unsaturated, the impedance of these windings is low, and due to theIrelatively large leakage current caused by the high loss iron used inthe cores of the magnetic amplifiers, the alarm lamp 16 is dimly lit toa point where it is just visible to the naked eye.

The present invention has provided an improved static elementannunciator circuit which is highly desirable from the standpoint ofsimplicity, reliability and iieXibility, particularly where a flashingsequence with a single alarm lamp is desired.

It should be understood that numerous modifications may be made of thepreferred forms of the invention illustrated and described withoutdeviating from the broader aspects of the invention.

What I claim as new and desire to protect by Letters Patent of theUnited States is:

1. An annunciator including: visual alarm means, condition responsivemeans having a normal variable indicating state and an abnormalyvariable indicating state, manually operable acknowledgement means, andcontrol circuit means responsive to said condition responsive means andsaid manually operable acknowledgement means to provide different alarmindications on said visual alarm means comprising: a first and a secondbistable circuit each comprised of a pair of static control elements andhaving two operating states, means for setting said irst bistablecircuit into one of its operating states when said condition responsivemeans is in its abnormal variable indicating state, means for operatingsaid visual alarm means to provide an initial -alarm indication whensaid tirst bistable circuit is in vsaid one operating state, and forproviding a normal indication thereon when said iirst bistable circuitis in its other operating state, means for setting said second bistablecircuit into one of its operating states when said manually operableacknowledgement means is operated, means for changing said initial alarmto an acknowledged alarm indication on said visual alarm means when saidsecond bistable circuit is in said one operating state, and means forsetting said irst and second bistable circuits into their otheroperating states after said lcondition responsive means is in its normalvariable indicating state.

2. An annunciator including: visual alarm means, condition responsivemeans having a normal variable indicating state and an abnormal variableindicating state, manually operable acknowledgement means, manuallyoperable vreset means, and control circuit means responsive to saidcondition responsive means and said manually operable acknowledgementand reset means to provide different alarm indications on said visualalarm means comprising. a lirst and a second bistable circuit eachcomprised of a pair of static control elements and having two operatingstates, means for setting said first bistable circuit into one of itsoperating states when said condition responsive means is in its abnormalvariable indicating state, means for operating said visual alarm meansto provide an initial alarm indication when said first bistable circuitis in said one operating state, and for providing a normal indicationthereon when said first bistable circuit is in its other operatingstate, means for setting said second bistable circuit into one of itsoperating states when manually operable acknowledgement means isoperated, means for changing said initial alarm to an acknowledged alarmindication on said visual alarm means when said second bistable circuitis in said one operating state, and means for setting said first andsecond bistable circuits into their other operating states when saidmanually operable reset means is operated and said condition responsivemeans is in its normal variabel indicating state.

3. An annunciator including: visual alarm means, condition responsivemeans having a normal variable indicating state and an abnormal variableindicating state, manually operable acknowledgement means, manuallyoperable reset means, and control circuit means responsive to saidcondition responsive means and said manually operable acknowledgementand reset means to provide different alarm indications on said visualalarm means comprising: a first and a second bistable circuit eachcomprised of a pair of static control elements and each having twooperating states, means for setting said first bistable circuit into oneof its operating states when said condition responsive means is in itsabnormal variable indicating state, means for operating said visualalarm means to provide an initial alarm indication when said firstbistable circuit is in said one operating state, and for providing anormal indication thereon when said first bistable circuit is in itsother operating state, means for setting said second bistable circuitinto one of its operating states when said manually operableacknowledgement means is operated, means for changing said initial alarmto an acknowledged alarm indication on said visual alarm means when saidsecond bistable circuit is in said one operating state, means forchanging said initial alarm on said visual alarm means to anacknowledged alarm indication when said scond bistable circuit is insaid one operating state, means for setting said first bistable circuitinto its other operating state when said manually operable reset meansis operated and said condition responsive means is in its normalvariable indicating state, and means for setting said second bistablecircuit to its oth-er operating state to cancel said acknowledged alarmindication when said first bistable circuit is triggered into said otheroperating state.

4. An annunciator including: visual alarm means, condition responsivemeans having a normal variable indicating state and an abnormal variableindicating state, manually operable acknowledgement means, and controlcircuit means responsive to said condition responsive means and saidmanually operable acknowledgement means to provide different alarmindica-tions on said visual alarm means comprising: a first staticelement bistable control circuit controlled by said condition responsivemeans and triggered into one operating state when said conditionresponsive means is operated to its abnormal variable indicating stateand triggered into its other operating state after said conditionresponsive means returns to its normal variable indicating state, asecond static element bistable control circuit controlled by saidmanually operable acknowledgement means and triggered into one operatingstate when said manually operable acknowledgement means is operated,means feeding a first energizing signal pulsating at a visible flashingrate to said visual alarm means to fiash the same only when said firstbistable circuit is in said one operating state, and means superimposinga' second energizing signal upon said first energizing signal to providea substantially constant indication on said visual alarm means only whensaid second bistable circuit is in said one operating state.

5. An annunciator including: visual alarm means, condition responsivemeans having a normal variable indicating state and an abnormal variableindicating state, manually operable acknowledgement means, manuallyoperable reset means, and control circuit means responsive to saidcondition responsive means and said manually operable `acknowledgementand reset means to provide different alarm indications on said visualalarm means comprising: a first static element bistable control circuitcontrolled by said condition responsive means and said manually op- Itrierable reset means and triggered into one operating state when saidcondition responsive means is 'operated to its abnormal variableindicating state and triggered into its other operating state when saidmanually operable reset means is operated and said condition responsivemeans returns to its normal variable indicating state, a second staticelement bistable control circuit controlled by said manually operableacgnowledgement means and said first bistable control circuit andtriggered into one operating state when said manually operableacknowledgement means is operated and into its other operating statewhen said first bistable circuit is triggered to said other operatingstate, means feeding a first energizing signal to said visual alarmmeans to provide an initial alarm indication only when said firstbistable circuit is in said one operating state, means feeding a secondenergizing signal to said visual alarm means to provide an acknowledgedalarm indication only when said second bistable circuit is in said oneoperating state, and means for setting said first and second bistablecircuits into their other operating states when said manually operablereset means is operated and said condition responsive means is in itsnormal variable indicating state.

6. An annunciator including: visual alarm means, condition responsivemeans having a normal variable indicating state and an abnormal variableindicating state, manually operable acknowledgement means, and controlcircuit means responsive to said condition responsive means and saidmanually operable acknowledgement means to provide different alarmindications on said visual alarm means comprising: a first staticelement bistable control circuit controlled by said condition responsivemeans and triggered into one operating state when said conditionresponsive means is operated to its abnormal variable indicating stateand triggered into its other operating state after said conditionresponsive means returns to its normal variable indicating state, asecond static element bistable control circuit controlled `by saidmanually operable acknowledgement means and said first bistable controlcircuit and triggered into one operating state when said manuallyoperable acknowledgement means is operated and triggered into its otheroperating state when said first bistable circuit is triggered to saidother operating state, means feeding a first energizing signal to saidvisual alarm means to provide an initial alarm indication only when saidfirst bistable circuit is in said one operating state, and means feedinga second energizing signal to said visual alarm means which effects anacknowledged alarm indication thereon only when said second bistablecircuit is in said one operating state.

7. An annunciator including: visual alarm means, condition responsivemeans having a normal variable indicating state and an abnormal variableindicating state, manually operable acknowledgement means, manuallyoperable reset mens, and control circuit means responsive to saidcondition responsive means and said manually operable acknowledgementand reset means to provide different alarm indications on said visualalarm means comprising: a first static element bistable control circuitcontrolled by said condition responsive means and said manually operablereset means and triggered into one operating state when said conditionresponsive means is operated to its abnormal variable indicating stateand triggered into its other operating state when said manually operablereset means is operated and said condition responsive means returns toits normal variable indicating stateJ a second static element bistablecontrol circuit controlled by said manually operable acknowledgementmeans and triggered into one operating state when said manually operableacknowledgement means is operated, means feeding a first energizingsignal pulsating at a visible fiashing rate to said visual alarm meansto fiash the same only when said first bistable circuit is in said oneoperating state, means superimposing a second energizing signal uponsaid first energizing signal to provide a resultant substantiallyconstant 17 indication si-gnal on said visual alarm means only when saidsecond bistable circuit is in said one operating state, and means forsetting said rirst bis-tabl-e circuit into its other operating statewhen said manually operable reset means is operated and said conditionresponsive means is in its normal variable indicating state.

8. An annunciator including: visual alarm means, condition responsivemeans having a normal variable indicating state and an abnormal variableindicating state, manually operable acknowledgement means, manuallyoperable reset means, and control circuit means responsive to saidcondition responsive means and said manually operable acknowledgementand reset means to provide different alarm indications on said visualalarm means comprising: a first static element bistable control circuitcontrolled by said condition responsive means and said manually operablereset means and triggered into one operating state Awhen said conditionresponsive means is operated to its abnormal variable indicating stateand triggered into its other operating state when said manually operablereset means is operated and said condition responsive means returns toits normal variable indicating state, a second static element bistablecontrol circuit controlled by said manually operable acknowledgementmeans and said iirst bistable control circuit and triggered into oneoperating state when said manually operable acknowledgement means isoperated, means feeding a iirst energizing signal pulsating at a visibleflashing rate to said visual alarm means to as'h thesame only when saidrst bistable circuit is in said one operating state, means superimposinga second energizing signal upon said irst energizing signal to provide aresultant substantially constant indication signal on said visual alarmmeans only when said second bistable circuit is in said one operatingstate, means for setting said iirst bistable circuit into its otheroperating state when said manually operable reset means is operated andsaid condition responsive means is in its normal variable indicatingstate, an audible alarm, a third static element bistable control circuitcontrolled by said condition responsive means and said manually operableacknowledgement means and operating independently of said first andsecond bistable control circuits, said third bistable control circuitbeing triggered into one operating state when said condition responsivemeans is in its abnormal variable indicating state and being triggeredinto its other operating state when said manuallyoperablepacknowledgement means is operated, and means for feeding anenergizing signal to said audible alarm only when said third bistablecircuit in said one operating state.

9. In an annunciator circuit including an alarm light, variableresponsive switch means having a normal variable indicating conditionand an abnormal variable indicating condition, and a source ofalternating current `for energizing said alarm light in response tooperation of said switch means from its normal to its abnormal variableindicating condition, the improvement in a circuit connected betweensaid switch means and said alarm light comprising: a saturable magneticdevice having a magnetic core with input and output windings on thecore, the output winding being connected between said alarm light andsaid source of .alternating current, a source of current for saturatingsaid core substantially continuously when fed to the input windingthereof, the impedance or the output winding when the `core is saturatedbeing sufciently low that a relatively large current flows through thealarm light to light the same brightly and the impedance thereof whenthe core is unsaturated being relatively high to provide a substantiallyie-energized condition of the alarm light, said core being made of ahigh-loss magnetic material wherein the leakage current underunsaturated core conditions is suiiicient to light the light, and meanscoupling said switch means to said source of saturating current and tosaid input winding to saturate said core when said switch means is inits abnormal variable indicating condition and to unsaturate the corewhen 'said switch means is in its normal variable indicating condition.

10. In an annunciator circuit including an lalarm light, a 1first set ofterminals for selective connection to a. set of normally-closed variableresponsive signal contacts, a second set of terminals for selectiveconnection to a 'se't of normally-open variable responsive signalcontacts, and a source of alternating current for energizing said alarmlight in response to opening of said normally-closed signal contacts orupon closure 'of said normally-open signal contacts, the improvement ina circuit connected between said iirst and second set of terminals andsaid alarm light comprising: a saturable magnetic device having amagnetic core with input and output windings on the core, the outputwinding being connected between said alarm light and said source ofalternating current, a source of current for saturating continuouslysaid core when fed to the input winding thereof, the impedance of theo-utput winding when the core is saturated being suniciently low that arelatively large current ilows through the alarm light to light the samebrightly and the impedance thereof when the core is unsaturated beingrelatively to provide a substantially de-energi'zed condition of thealarrri light, said core being made of a high-loss magnetic materialwherein the leakage current under unsaturated core conditions issuflicient to light the alarm light dimly to a point where it is visibleto the naked eye, a current-limiting resistor, means connecting saidcurrent-limiting resistor and said second set of terminals between saidinput winding and said source of saturating current, means connectingsaid iirst set of terminals in series with said current-limitingresistor and in shunt with said input winding whereby saturating currentis shunted around the input winding as long as the signal contacts areclosed, said source of saturating current being cie-coupled from saidinput winding when said normally-open contacts are open.

ll. In an annunciator circuit including `an alarm light, a first set ofterminals for selective connection to a set of normally-closed variableresponsive signal contacts, a second set of terminals for selectiveconnection` to a set of normally-open variable responsive signalcontacts, and a source of alternating current r'or energizing said alarmlight in response to opening of said normally-closed signal contacts orupon closure of said normally-open signal contacts, the improvement in acircuit connected between said first and second set of terminals andsaid alarm light comprising: a saturable magnetic device having amagnetic core with input and output windings on the core, the inputWinding being connected between said alarm light and said source ofalternating current, a source of current for saturating continuouslysaid core when fed to the input winding thereof, the impedance of theoutput winding when the core is saturated being suiliciently low that `arelatively large current ows through the alarm light to light the samebrightly and the impedance thereof when the core is unsaturated beingrelatively high to provide a substantially de-energized condition of thealarm light, a current-limiting resistor, means connecting saidcurrent-limiting resistor and said second set of terminals between saidinput winding and said source of saturating current, and meansconnecting said nrst set of terminals in series `with saidcurrent-limiting resistor and in shunt with said input winding rwherebysaturating current is shunted around the input Winding as long as thesignal contacts are closed, said source of saturating current beingde-coupled from said input winding when said normally-open contacts areopen.

l2. In an annuniciator circuit including an alarm light, variableresponsive means having a normal variable indicating condition and anabnormal variable indicating condition, and a manually operableacknowledgement switch, the improvement in a circuit for providing aashing indication on said alarm light when the variable responsive meansis in its abnormal indicating condition and a steady indication thereonupon subsequent operation of saidv acknowledgement switch, said circuitcomprising: a first signal source for providing a current of anamplitude varying at a visible flashing rate, a second signal source forproviding a current of relatively constant amplitude, a saturablemagnetic control device having a magnetic core with input and outputwindings on the core, said output winding being connected in series withsaid alarm light and a source of energizing current pulses, theimpedance of said output winding when the associated core is saturatedbeing relatively low to provide energizing current which lights thealarm light brightly, first gating means connected between said firstsignal source and the input winding of said magnetic control device,second gating means connected between said second signal source and saidinput winding to feed current from said second signal source to saidinput winding, means responsive to the `abnormal variable indicatingcondition of said variable responsive means by opening said first gatingmeans to pass the current therefrom to said input winding tosuccessively saturate and unsaturate the core at a visible flashing rateto flash said alarm light, and means responsive to operation of saidacknowledgement switch by opening said second gating means to passcurrent therefrom to said input winding to saturate the coresubstantially continuously to light the alarm light continuouslybrightly.

13. In an annunciator circuit including an alarm light, variableresponsive means having a normal variable indicating condition and vanabnormal variable indicating condition, and a manually operableacknowledgement switch, the improvement in a circuit for providing aflashing indication on said alarm light when the variable responsivemeans is in its abnormal indicating condition and a steady indicationthereupon subsequent operation of said acknowledgement switch, saidcircuit comprising: a first signal source for providing a current of anamplitude varying at a visible flashing rate, a second signal source forproviding a current of relatively constant amplitude, a saturablemagnetic control device having a magnetic core with input and outputwindings on the core, said output winding being connected in series withsaid alarm light and a source of energizing current pulses, theimpedance of said output winding 'when the associated core is saturatedbeing relatively low to provide energizing current which lights thealarm light brightly, said core being made of a high-loss magneticmaterial wherein the current fiowing in the output winding underunsaturated core conditions where the impedance of the output winding isrelatively high and is yet sufficient to light the alarm light dimly toa point that it is visible to the naked eye, first gating meansconnected between said first signal source and the input winding of saidmagnetic control device, second gating means connected between saidsecond signal source and said input winding to feed current from saidsecond signal source to said input winding, means responsive to theabnormal variable indicating condition of said variable responsive meansby opening said first gating means to pass the current therefrom to saidinput winding to successively saturate and unsaturate the core at avisible flashing rate to flash said alarm light, and means responsive tooperation of said acknowledgement switch by opening said second gatingmeans to p-ass current therefrom to said input winding to saturate thecore substantially continuously to light the alarm lights continuouslybrightly.

` 14. An annunciator comprising an alarm light, manually operableacknowledgement means, and control circuit means responsive to saidcondition responsive means and saidfacknowledgement means forcontrolling said alarm light means comprising: a first and a secondstatic element bistable circuit each having two operating states, meansfor operating said first bistable circuit to one of its operating stateswhen said condition responsive means is changed from its normal to itsabnormal variable indicating state, means for setting said secondbistable circuit into one of its operating states when said manuallyoper-able acknowledgement means is operated, a saturable control devicehaving an input which operates the control device in a first state ofoper-ation when the signal fed thereto has an amplitude exceeding agiven value and operates the control device in a second state ofoperation when the amplitude of a signal given thereto is below saidamplitude, means responsive to operation of said first bistable controlcircuit in said one operating state by coupling to said input signalswhose amplitude exceed said given value at a visible flashing rate sothat the saturable control device is saturated at a visible liashingrate, means responsive to the operation of said second bistable controlcircuit to said one operating state for feeding to said input acontinuous signal which continuously saturates the control device, andcircuit means connecting said alarm light to said saturable controldevice to energize the alarm light when the control device is in one ofsaid states of operation and to de-energize the alarm light when thecontrol device is in its other state of operation.

15. In an annunciator circuit including -a first and a second bistablecircuit, each bistable circuit comprising: a first `and a secondmagnetic core not gate stage, each not gate stage including a magneticcore unit with windings thereon, a main signal input terminal, a notcontrol signal input terminal and a signal output terminal, signalvoltage means connected to said main signal input terminals of saidfirst and second not gate stages, said iirst and second magnetic notgate stages each further including means connecting said variousassociated terminals to the associated core windings so that appreciablesignals from said voltage means appear at the associated signal outputterminal if a no-signal condition exists at the associated controlsignal input terminal, and a relatively no-signal output conditionexists at the associated signal output terminal if a signal conditionexists at the associated not signal input terminal, means connectingsaid signal output terminal of each not gate stage to the control signalinput terminal of the other not gate stage, whereby the output conditionof each not gate stage controls the output condition of the other notgate stage; variable responsive switch means having abnormal and normalvariable indicating conditions, rst circuit means connecting thevariable responsive switch means to the control signal input terminal ofthe first not gate stage of the first bistable control circuit forfeeding a signal thereto to provide a no-signal output condition thereofwhen the variable responsive switch means is in its abnormal variableindicating condition, the latter gate stage being in a signal outputcondition when the variable responsive switch means is in its normalvariable indicating condition, manually operable acknowledgement switchmeans, second circuit means connecting said acknowledgement switch meansto the control signal input terminal of the not gate stage of the secondbistable control circuit which is normally not a signal output conditionfollowing the initial triggering of said first gate stage of the first4bistable control circuit into a no-signal output condition, said secondcircuit means effecting the feeding of -a signal to the control signalinput terminal'of the first not gate stage of the second bistablecontrol circuit to trigger the same into a no-signal output condition,and visual alarm means, and means connecting said visual alarm means toboth of said bistable control circuits to provide an initial alarmindication when the first bistable control circuit has been initiallytriggered by operation of said variable responsive switch means, and toprovide an acknowledged alarm indication when said second bistablecircuit has been triggered by said acknowledgement switch means.

16. In an annunciator circuit including a first and a second bistablecircuit, each bistable circuit comprising: a first and a second magneticcore not gate stage, each not" gate stage including a magnetic core unit-with windings thereon, a main signal input terminal, a not controlsignal input terminal and a signal output terminal,

signal lvoltage means connected to said main signal input terminals ofsaid first and second not gate stages, said first landksecond magneticnot gate stages each further including means connecting said variousassociated terminals to the associated core windings so that appreciablesignals from said signal voltage means appear at the associlated signaloutput terminal if a no-signal condition exists at the -associatedcontrol signal input terminal, and a relatively no-signal outputcondition exists at the associated signal output terminal if a signalcondition exists 'at the associated not signal input terminal, meansconnecting said signal output terminal of each not gate stage to thecontrol signal input terminal of the other not gate stage, whereby theoutput condition of each not gate stage controls the output condition ofthe other not gate stage; variable responsive switch means havingabnormal and normal variable indicating conditions, irst circuit meansconnecting the variable responsive switch means to the control signalinput terminal of the :[irst not gate stage of the first bistablecontrol circuit for feeding a continuous signal thereto to provide andmaintain a no-signal output condition thereof when the variableresponsive switch means is in its abnormal variable indicatingcondition, the latter gate stage being in a signal output `conditionwhen the variable responsive switch means is in its normal variableindicating condition, manually operable Iacknowledgement switch means,second circuit means connecting said acknowledgement switch means to thecontrol signal input terminal of the not gate stage of the secondbistable control circuit which is normally not a signal output conditionfollowing the initial triggering of said rst gate stage of the firstbistable control circuit into a no-signal output condition, said secondcircuit means effecting the feeding of a momentary signal to the controlsignal input terminal of the first not gate stage of the signal bistablecontrol circuit to trigger the same into a no-signal output condition,manually operable reset switch means, third circuit means connecting thereset switch means to the control signal input terminal of the secondnot gate stage of the lirst bistable control circuit for connecting amomentary signal thereto upon momentary operation of the reset switchmeans to provide a no-signal output condition thereof provided saidvariable responsive switch means has returned to its normal variableindicating condition, and visual alarm means, and means connecting saidvisual -alarm means to both off said bistable control circuits toprovide an initial alarm indication when the first bistable controlcircuit has been initially triggered by operation of said variableresponsive switch means to provide an acknowledged alarm indication whensaid second bistable circuit has been triggered by said acknowledgementswitch means and to provide a normal visual indication when operation ofsaid manual reset switch means is effective to trigger said firstbistable control circuit.

17. An annunciator circuit comprising: variable responsive meansdirectly to the variable rand having a normal condition when thevariable is abnormal, manually operable acknowledgement switch means,manually operable reset switch means, visual alarm means, and a controlcircuit responsive to said variable responsive means and saidacknowledgement and reset switch means for providing an initial visualalarm indication on said visual alarm means when the variable responsivemeans is operated to its abnormal condition by the 'associated variableand a different acknowledged visual alarm indication thereon when saidacknowledgement switch is operated, said control circuit comprising afirst and a second pair of current control devices each forming a notgate control circuit having not signal input terminals and a gatedsignal output terminal and related means interconnecting the same toform first and second bistable circuits each having a rst and a secondstate of operation, means coupling said variable responsive means to thenot signal input terminal of one of the current control devices of saidrst bistable control circuit for effecting the triggering of the circuitformed thereby from its rst to its second state of operation when saidvariable responsive means is operated to said abnormal condition and tothen maintain this state of operation at least until said variableresponsive means is returned to its normal condition, means couplingsaid acknowledgement switch means to the not signal input terminal ofone of the current control devices of the second bistable circuit foreffecting the triggering thereof from a first to a second state ofoperation upon momentary operation of said latter switch means, meansinterconnecting the rst and second bistable circuits for effecting thetriggering of the second bistable circuit into its rst state ofoperation when the first bistable circuit is triggered into one of itsstates of operation, means coupling said visual alarm means to saidcontrol circuit to provide an initial visual alarm indication when thefirst bistable circuit is in its second state of operation and thesecond bistable circuit in its first state of operation, and to providesaid acknowledged visual alarm indication when the first bistablecircuit is in its second state of operation and the second bistable`circuit is in its second state of operation, and means coupling saidreset switch means to the not signal input terminal of one of thecurrent control devices of said first bistable circuit for effecting thetriggering thereof from its second back to its first state of operationupon momentary operation of said reset switch means provided saidvariable responsive means has returned to its normal condition.

18. In an `annunciator circuit including an alarm light, a first set ofterminals for selective connection to a set of normally-closed variableresponsive signal contacts, and a source of alternating current forenergizing said alarm light in response to opening of saidnormallyclosed signal contacts, the improvement in a circuit connectedbetween said iirst set of terminals and said alarm light comprising: asaturable magnetic device having a magnetic core with input and outputwindings on the core, the output winding being connected between saidalarm light and said source of alternating current, a source of currentfor saturating continuously said core when fed to the input windingthereof, the impedance of the output winding when the core is saturatedbeing sufficiently low that a relatively large current ilows through the'alarm light to light the same brightly and the impedance thereof whenthe core is unsaturated being relatively high to provide a substantiallyde-energized condition of the alarm light, a current-limiting resistor,means connecting said current-limiting resistor between said inputwinding and said source of saturating current, and means connecting saidfirst set of terminals in series with said current-limiting resistor andin shunt with said input winding whereby saturating current is shuntedaround the input winding as long as the signal contacts are closed.

References Cited in the file of this patent UNITED STATES PATENTS

